Triple-band nonreciprocal optical Tamm states in a Weyl-semimetal/Fibonacci-type photonic heterostructure

Conventional optical Tamm state (OTS) structures suffer from reciprocity and a single resonant mode, severely hindering their potential in multichannel nonreciprocal photonics. Here, we demonstrate triple-band nonreciprocal OTS resonances in a Weyl semimetal (WSM)/Fibonacci-type photonic heterostructure in the mid-infrared range. The Fibonacci reflector provides multiple photonic band gaps, while the WSM layer acts as the metallic boundary for OTS and yields an axial-vector-induced anomalous Hall effect breaking time-reversal symmetry. Transfer-matrix calculations reveal three sharp transmission resonances near the band gaps, each coinciding with a reflection minimum, phase zero crossing, and localized electric-field distributions, supporting their OTS origin. Reversing the incidence direction shifts resonance frequencies and transmittance peaks, producing triple-band nonreciprocity due to the WSM's gyrotropic response, altering phase accumulation and interfacial matching. The axial vector governs the nonreciprocal strength, while the Fermi energy, incident angle, and layer thicknesses affect the resonance positions and forward-backward contrast. These results provide a route toward multichannel nonreciprocal filtering and angle-sensitive photonic devices that operate without an external magnetic field.